Nested assemblages of Orthoptera species in the Netherlands: the importance of habitat features and life‐history traits

Abstract

Aim Species communities often exhibit nestedness, the species found in speciespoor sites representing subsets of richer ones. In the Netherlands, where intensification of land use has led to severe fragmentation of nature, we examined the degree of nestedness in the distribution of Orthoptera species. An assessment was made of how environmental conditions and species life-history traits are related to this pattern, and how variation in sampling intensity across sites may influence the observed degree of nestedness.Location The analysis includes a total of 178 semi-natural sites in the Pleistocene sand region of the Netherlands.Methods A matrix recording the presence or absence of all Orthoptera species in each site was compiled using atlas data. Additionally, separate matrices were constructed for the species of suborders Ensifera and Caelifera. The degree of nestedness was measured using the binmatnest calculator. binmatnest uses an algorithm to sort the matrices to maximal nestedness. We used Spearman's rank correlations to evaluate whether sites were sorted by area, isolation or habitat heterogeneity, and whether species were sorted by their dispersal ability, rate of development or degree of habitat specificity.Results We found the Orthoptera assemblages to be significantly nested. The rank correlation between site order and sampling intensity was high. The degree of nestedness was lower, but remained significant when under-and oversampled sites were excluded from the analysis. Site order was strongly correlated with both size of sample site and number of habitat types per site. Rank correlations showed that species were probably ordered by variation in habitat specificity, rather than by variation in dispersal capacity or rate of development of the species.Main conclusions Variation in sampling intensity among sites had a strong impact on the observed degree of nestedness. Nestedness in habitats may underlie the observed nestedness within the Orthoptera assemblages. Habitat heterogeneity is closely related to site area, which suggests that several large sites should be preserved, rather than many small sites. Furthermore, the results corroborate a focus of nature conservation policy on sites where rare species occur, as long as the full spectrum of habitat conditions and underlying ecological processes is secured.

Defining hotspots of characteristic species for multiple taxonomic groups in the Netherlands

“…For the five species groups studied here, these regions comprise the majority of the species present in the Netherlands, since these regions automatically incorporate the more common and widely distributed species too. This phenomenon of nestedness in species composition was observed earlier for Orthoptera in the Netherlands (Schouten et al 2007). …”

Experimental evidence for density-determined wing dimorphism in two bush-crickets (Ensifera: Tettigoniidae)

“…Marshall & Haes, 1988;Fartmann, 1997;Thomas et al, 2001). For our experiments we used two related bush-cricket species (M. roeselii and M. brachyptera) that vary in their habitat requirements and their propensity to produce long-winged individuals in nature: While macropterous individuals of the habitat specialist M. brachyptera are rare and are never observed outside the mating habitat (Schouten et al, 2007), longwinged individuals of the habitat generalist M. roeselii occur regularly (e.g. Thomas et al, 2001;Simmons & Thomas, 2004;Poniatowski & Fartmann, 2008b).…”

Nested species subsets of amphibians and reptiles in Thousand Island Lake

“…全貌 (Wright et al, 1998)。因此, 对于不同栖息地类 型中不同类群的嵌套格局还需要进一步的分析和 研究。 目前已有很多机制用来解释嵌套格局的形成 原 因 (Schoener & Schoener, 1983;Blake, 1991;Baber et al, 2004;Higgins et al, 2006), 主要有 4 种假 说在当前占主导地位 (Wright et al, 1998;Chen & Wang, 2004) ： (1) 选择性迁移假说(the selective colonization hypothesis)：由于物种扩散能力的差异, 扩散能力强或弱的多数物种都可占领大岛屿; 而扩 散能力强的少数物种占领小岛屿,从而形成嵌套格 局 (Bird & Boecklen, 1998;Cook & Quinn, 1995;Conroy et al, 1999;Loo et al, 2002;Mac Nally et al, 2002)。(2) 选择性灭绝假说(the selective extinction hypothesis)： 岛屿面积大小制约物种分布, 要求较大 的最小面积的物种,或具有较小种群的物种, 可能 会从不同面积的岛屿生境中首先灭绝, 从而形成嵌 套格局 (Patterson & Atmar, 1986;Bolger et al, 1991;Cutler, 1991;Lomolino, 1996)。 (3) 生境嵌套假说 ( the habitat nestedneass hypothesis)：物种分布与生 境密切相关,即嵌套格局是岛屿生境结构呈现嵌套 格局的结果 (Blake, 1991;Calmé & Desrochers, 1999;Honnay et al, 1999;Ficetola & Bernardi, 2004)。 (4) 被动抽样假说(the passive sampling hypothesis)：不 同生境中, 物种多度存在较大差异,因此在抽取样 本时,多度高的物种被抽中的概率大; 在不同取样 面积下, 数量丰富的物种在小面积中出现的概率和 在大面积的抽样中出现的概率都大,反之亦然。 因此, 不同取样面积的一系列物种组合自然就形成了嵌 套结构 (Cutler, 1994;Lomolino, 1996;Andrén, 1994;Nielsen & Bascompte, 2007)。4 种假说中, 除"被动 抽样"与物种间多度差异和抽样强度有关 (Schouten et al, 2007) Wright et al, 1998;Fleishman et al, 2002;Schouten et al, 2007)。 在自然生态系统中, 两栖爬行类占有重要地 位。研究表明, 全球两栖爬行类正以超过自然灭绝 的高速率灭绝 (Stuart et al, 2004;Whitfield et al, 2007), 这与生境丧失和片段化有直接关系 (Chen & Li, 1990;Pan et al, 2002 …”